1. Field of the Invention
The present invention relates to a clock signal generating circuit for a semiconductor large scale integrated circuit.
2. Description of the Related Art
In the field of the semiconductor large scale integrated (LSI) circuit, the clock signal generating circuit (below, clock generator) is widely used for synchronous operations among a central processing unit, memories and interface units. Accordingly, it is necessary to generate clock signals having a precise timing from the clock generator in order to carry out these synchronous operations. Moreover, the operating speed of these units depends on the clock rate (i.e., clock generating speed from the clock generator). Particularly, the logic operations of the LSI circuit greatly depend on this clock rate.
Therefore, it is necessary to realize extremely precise, high speed, and highly reliable clock signals for synchronous operations in the LSI circuit.